Re: A small question about Device Mapper

[Doug Dumitru <doug@xxxxxxxxxx>]

Xun,

This is a little off-topic for this list.  Device mapper is the low level structure to create the devices.  Configuration is done in user space and is more a topic for system startup people (is there a sysinit list?).

Regardless, I will try to help.

Exactly how and where you do this depends a lot of your environment and when you need the dm device to become available.  You basically have to include your dmsetup command in the startup scripts early enough to meet your needs.

In some cases, this might be all the way into initramfs (or initrd depending on your distro).  This would start the dm device before even your root file system mounted.

You might be able to start the device later, which implies a system "service" that runs as a part of the boot.  If you can take the start very late, you might want to consider just adding it to rc.local (most distros still support this), which runs last.  This would go into /etc/init.d/rc.local (again, your distro may vary).

Doug

On Sun, Aug 23, 2015 at 12:29 AM, Ni, Xun <xun.ni@xxxxxxxxx> wrote:

Hi, all:

 

I use device mapper to config a thin-provision for a block device, with dmsetup, with the following command:

 

Dmsetup create pool –table “0 `blockdev –getsize /dev/sdd1` thin-pool /dev/sdd2 /dev/sdd1 128 0”

Dmsetup message /dev/mapper/pool 0 “create_thin 0”

Dmsetup create snap1 –tabe “0 `blockdev –getsize /dev/sdd3` thin /dev/mapper/pool 0 /dev/sdd3”

 

Everything works well, but when I reboot the system, the block device is gone, I need to create the pool again…

 

Anyone has idea on how to make this config persistent?  I need to boot the kernel , the dm pool device shows after the MD device found.

 

Thanks,

Xun

 

--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel

--

Doug Dumitru
EasyCo LLC

--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel